Program Information
Development and Applicability of a New Elastic Immobilization with Metal Markers for Postoperative Radiotherapy for Breast Cancer
T Fujimoto1*, M Yoshimura2 ,M Shioji1 , H Asada3 , Y Ishihara2 , K Hirata2 , Y Ono2 , Y Miyamae1 , S Yano1 , M Nakata1 , K Higashimura1 , T Mizowaki2 , (1) Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto, Japan (2) Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Kyoto, Japan (3) Kyoto University Hospital Nursing Administration, Kyoto, Japan
Presentations
TU-C3-GePD-TT-2 (Tuesday, August 1, 2017) 10:30 AM - 11:00 AM Room: Therapy ePoster Theater
Purpose: The purpose of this study was to develop an elastic immobilization with metal markers for postoperative radiotherapy for breast cancer.
Methods: An elastic immobilization for the supine position was developed with a commercially available bra. This elastic immobilization had seven small metal markers to improve patient setup accuracy.First, the surface and reference doses for X-ray and electron beams were measured using ionization chambers, a water-equivalent phantom, and an elastic immobilization.Influences of dose attenuation with immobilization were estimated using measured doses. Next, the reproducibility for the immobilization position was evaluated using a human phantom and elastic immobilization. Landmarks were drawn on the human phantom to indicate positional relationship between the immobilization and body, and then several x-ray images were produced. The reproducibility with the landmarks was compared with that without landmarks using the displacement from the metal markers.Furthermore, structure similarity (SSIM) indexes were calculated using several CT sets to evaluate the difference in breast shape under the same conditions.
Results: By using the immobilization, the surface dose was increased by 4.0% at maximum. The attenuation of X-ray beams and electron beams was less than 2%. When using the landmarks, the displacement of the metal marker was 0.53 ± 0.28 cm. The SSIM index with and without landmarks was 0.900 (0.897-0.902) and 0.724 (range 0.559-0.928), respectively. The utilization of landmarks decreased the displacement of the metal markers and showed the possibility to stabilize the breast shape.
Conclusion: This study showed the dose characteristics and position accuracy for radiotherapy for breast cancer patients with immobilization with metal markers, which could provide positional accuracy on the setup with minimum skin markers and may be useful for reducing the physical and psychological burden for patients.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by JSPS KAKENHI grant number JP16K19229
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